1. Field of the Invention:
The present invention relates to a ribbon feeding device for feeding a ribbon of an ink ribbon cassette, which is detachably mounted on at carriage, in one way.
2. Description of Related Art:
There is known a ribbon feeding device having a rack extending in the moving direction of a carriage, a V-shaped arm having a proximal end pivotally mounted on a pivot on the carriage, a pinion rotatably mounted on one distal end of the arm and meshing with the rack, and a ribbon winding mechanism operatively connected to the pinion, so as to rotate a winding shaft of the ribbon winding mechanism by the rotational force of the pinion in mesh with the rack by the movement of the carriage, from Japanese Patent Laid-Open Publication No. Hei 5-562.
In this ribbon feeding device, the other distal end of the arm is connected to a printing-head-mounting plate on which a printing head is mounted, and an approaching/retracting mechanism is provided for moving the printing-head-attaching plate toward and away from a platen with respect to the carriage. When the printing head is moved toward the platen by the approaching/retracting mechanism, the one distal end of the arm is moved toward the rack so that the pinion is brought into engagement with the rack, to operate the ribbon winding mechanism to wind the ribbon. When the printing head is retracted away from the platen by the approaching/retracting mechanism, the one distal end of the arm is moved away from the rack so that the pinion is brought out of engagement with the rack, so as to make the ribbon winding mechanism inoperative not to wind the ribbon.
A printer is known from Japanese Patent Laid-Open Publication No. Hei 6-340159, in which a carriage for carrying a printing head is slidably fitted on a guide shaft to be moved longitudinally of the platen and the carriage is also moved toward and away from the platen in accordance with the thickness of the individual paper sheet by an eccentric angular movement of the guide shaft so as to print on various kinds of paper sheets of differing thicknesses. A pinion is provided on the carriage to be engaged with a rack extending in the moving direction of the carriage in front of the guide shaft and is rotated by the longitudinal movement of the carriage, so that an ink ribbon of the ink ribbon cassette on the carriage is fed by the rotating force of the pinion. A cassette-attaching base mounted on the carriage is slidably engaged with the rack, and the rack is arranged slightly movable in the direction toward and away from the platen and is urged away from the carriage by a spring to keep the pinion in mesh with a rack while the carriage is moved toward and away from the platen.
The rack has first and second guide grooves along its length for engaging the rack with the carriage in this printer, and the cassette-attaching base mounted on the carriage has first and second rack-engaging ridges to be fitted in the first and second guide grooves, respectively, so that the front wall of the rack is sandwiched between the first and second rack-engaging ridges.
Further, a slider for rotatably supporting the pinion is slidably fitted to the first and second guide grooves, respectively, and the pinion has a large-diameter-gear section meshing with the rack and a small-diameter-gear section operatively connected to a ribbon feed mechanism.
According to the above arrangement, in order to prevent the pinion from coming out of engagement with the rack, it is necessary to provide the rack with the first and second guide grooves and to provide the cassette-attaching base with the first and second rack-engaging ridges as well as the sliders. Therefore, the apparatus is complex in structure and hence expensive to manufacture. Further, since the cassette-attaching base has to be engaged with the rack and the slider has to be slidably fitted to the first and second guide grooves, assembling of the device would be laborious and time-consuming.